Les proprietes electriques des fibres de carbone et leur interpretation sur la base d'un modele structurel

Abstract

The electrical conductivity and thermoelectric power of rayon-based carbon fibers have been measured from liquid helium temperature to 1000°K on samples with various orientations and HTT. The measurements of the conductivities of interstitial compounds of these fibers with potassium show a large increase in density of free carriers due to the intercalation of metal atoms without significant modification of the mobility. The results are explained by using a band model which includes localized states and a mobility gap related to the microstructure of the fibers. It is shown that the density of free carriers is dependent on the number of local defects acting as acceptor centers. The mobility, practically independent of electron-phonon interactions, is limited essentially by scattering on structural defects. This concept is used to explain the conduction properties of carbon fibers saturated with potassium and to evaluate the mobility of the electrons in these compounds.